Mr. Clancy, who grew up in Baltimore, died at Johns Hopkins Hospital after a brief illness, his lawyer, J. W. Thompson Webb, said on Wednesday. Neither Mr. Webb nor Mr. Clancy’s longtime publisher, Ivan Held, president of G. P. Putnam’s Sons, said he knew the precise cause of death.
Mr. Clancy’s debut book, “The Hunt for Red October,” was frequently cited as one of the greatest genre novels ever written. With the book’s publication in 1984, Mr. Clancy introduced a new kind of potboiler: an espionage thriller dense with technical details about weaponry, submarines and intelligence agencies.
It found an eager readership. More than 100 million copies of his novels are in print, and a remarkable 17 have reached No. 1 on the New York Times’s best-seller list, including “Threat Vector,” released last December. Prolific until his death, Mr. Clancy had been awaiting publication of his next book, “Command Authority,” set for Dec. 3.
The impact of his books has been felt far beyond the publishing world. Some were adapted by Hollywood and became blockbusters starring Harrison Ford, Alec Baldwin and Ben Affleck as Mr. Clancy’s hero protagonist, Jack Ryan. Mr. Clancy arranged for his thrillers to be turned into video games that were so realistic, the military licensed them for training. And on television, fast-paced espionage using high-tech tools in the Clancy mold found a place in popular shows like “24” and “Homeland.”
The enterprises made Mr. Clancy a millionaire many times over and a familiar figure on the pop-culture landscape, frequently seen in photographs wearing a baseball cap and aviator sunglasses and holding a cigarette. With his riches he acquired an 80-acre farm on the Chesapeake Bay. He became a part owner of the Baltimore Orioles. He even bought a tank.
It was all a far cry from his days as a Maryland insurance salesman writing on the side in pursuit of literary aspirations and submitting his manuscript for “The Hunt for Red October” to the Naval Institute Press in Annapolis, Md. An editor there, Deborah Grosvenor, became mesmerized by the book, a cold war tale set on a Soviet submarine.
But she had a hard time persuading her boss to read it; Mr. Clancy was an unknown, and the publisher had no experience with fiction. She was also concerned that the novel had too many technical descriptions, and asked Mr. Clancy to make cuts. He complied, trimming at least 100 pages while making revisions.
“I said, ‘I think we have a potential best seller here, and if we don’t grab this thing, somebody else would,’ ” Ms. Grosvenor, now a literary agent, said in an interview on Wednesday. “But he had this innate storytelling ability, and his characters had this very witty dialogue. The gift of the Irish, or whatever it was — the man could tell a story.”
The press paid $5,000 for the book, publishing it in 1984.
“The Hunt for Red October” became a runaway best seller when President Ronald Reagan, who had been handed a copy, called it “my kind of yarn” and said that he couldn’t put it down.
But its details about Soviet submarines, weaponry, satellites and fighter planes raised suspicions. Even high-ranking members of the military took notice of the book’s apparent inside knowledge. In a 1986 interview, Mr. Clancy said, “When I met Navy Secretary John Lehman last year, the first thing he asked me about the book was, ‘Who the hell cleared it?’ ”
No one did, Mr. Clancy insisted; all of his knowledge came from technical manuals, interviews with submarine experts and books on military matters, he said. While he spent time on military bases, visited the Pentagon and dined with military leaders, he said, he did not want to know any classified information.
“I hang my hat on getting as many things right as I can,” Mr. Clancy once said in an interview. “I’ve made up stuff that’s turned out to be real — that’s the spooky part.”
Thomas Leo Clancy Jr. was born into a middle-class Baltimore family on April 12, 1947. As a boy he skipped over children’s literature to read naval history, poring over journals and books intended for career military officers and engineering experts.
He attended Loyola College in Baltimore, where he majored in English, and graduated in 1969. While he harbored ambitions to serve in the military — he joined the Army R.O.T.C. — he was told he was too nearsighted. He began working instead at a small insurance agency founded by his wife’s grandfather in rural Maryland, a line of work he was happy to abandon after he found success as an author.
He followed “The Hunt for Red October” with “Red Storm Rising” in 1986, “Patriot Games” in 1987, “The Cardinal of the Kremlin” in 1988 and “Clear and Present Danger” in 1989.
The critical reception was warm from the start. Reviewing “Red Storm Rising” in The Times in 1986, Christopher Lehmann-Haupt wrote that the book “far surpassed” Mr. Clancy’s debut novel.
“Red Storm Rising” is a “superpower thriller,” Mr. Lehmann-Haupt wrote, “the verbal equivalent of a high-tech video game.”
Some critics questioned the unwavering virtuousness of many of Mr. Clancy’s heroes, particularly Jack Ryan.
“All the Americans are paragons of courage, endurance and devotion to service and country,” Robert Lekachman wrote in The Times in 1986. “Their officers are uniformly competent and occasionally inspired. Men of all ranks are faithful husbands and devoted fathers.”
Mr. Clancy is survived by his second wife, Alexandra Llewellyn Clancy, and their daughter, Alexis Jacqueline Page Clancy. He had four children from his first marriage: Michelle E. Bandy, Christine C. Blocksidge, Thomas L. Clancy III and Kathleen W. Clancy.
Besides the planned publication of his next book, “Command Authority,” a movie prequel about Jack Ryan’s pre-C.I.A. days, “Jack Ryan,” will be released on Christmas and stars Chris Pine as Ryan.
Mr. Clancy said none of his success came easily, and he would remind aspiring writers of that when he spoke to them.
“I tell them you learn to write the same way you learn to play golf,” he once said. “You do it, and keep doing it until you get it right. A lot of people think something mystical happens to you, that maybe the muse kisses you on the ear. But writing isn’t divinely inspired — it’s hard work.”